Magnetic clutch structure



' May 29, 1962 A. F. MILLINGTON ETAL 3,035,679

MAGNETIC CLUTCH STRUCTURE Filed Jan. i7, V1958 2 Sheets-Sheet 1 I N (1) co il co I IN V EN TORS ALFRED EMILLINGTON y GERARD E. HEBERT May 29, 1962 Filed Jan. 17, 1958 2 Sheets-Sheet 2 g 11:11:- 111i FF" 1 t I, 8

Y! S g 9 r I Q Q g i (I) I III Q\\gr 7 I .1 I g (A (A u N I v g9 gwco co co 1:) 0 VVO m fifi 8% 0 INVENTORS ALFRED F. MILLINGTON BY GERA ATTORNEYS 3,36,679 Patented May 29, 19 52 ice 3,036,679 MAGNETIG CLUTCH STRUCTURE Alfred F. Miliington, Northvilie, and Gerard E. Hebert, Livonia, Mich, assignors to Novi Equipment Company, Novi, Mich, a corporation of Michigan Filed Jan. 17, 1958, Ser. No. 709,502 6 Clairns. (Ci. i92-84) The present invention relates to a magnetic clutch structure.

It is an object of the present invention to provide a magnetic clutch including concentric rotatable driving and driven members, a movable clutch plate carried by one of said members for moving axially thereof into engagement with the other of said members while preserving torque transmitting relation therewith, for establishing a magnetic flux which links said clutch plate and the adjacent portion of said other member.

More specifically, it is an object of the present invention to provide a structure as described in the preceding paragraph in which the field windings are stationary.

it is a further object of the present invention to provide magnetic clutch structure including a shaft, a cupling member connected to said shaft, an annular clutch plate movably connected to said coupling member in torque transmitting relation, a driving member carried for rotation by said coupling member and having a clutch portion in close axially spaced relation to said clutch plate.

It is a further object of the present invention to provide structure as described in the preceding paragraph in which said driving member includes a rim portion formannular housing.

It is a further object of the present invention to pro vide in a magnetic clutch, an annular member having a radially outwardly extending flange, a clutch plate having a radially inwardly extending flange, elongated leaf springs having opposite ends connected to said flanges and adapted to provide for axial movement between said annular member and clutch plate and to transmit torque therebetween.

stantially at the faces of the pole pieces.

Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawings, illustrating preferred embodiments of the invention, wherein:

FIGURE 1 is an elevational view of drive structure including the magnetic clutch.

FIGURE 2 is a sectional view on the line 22 FIG- URE l, with some elements circumferentially displaced for clarity.

FIGURE 3 is a fragmentary elevational view of the torque transmitting resilient connection to the clutch plate.

FIGURE 4 is a fragmentary section on the line 4-4, FIGURE 3.

FIGURE 5 is a sectional view through a clutch representing a different embodiment of the present invention.

FIGURE 6 is a front elevational view of the movable pole piece or clutch plate.

The present invention is capable of many different applications but is illustrated herein as applied to a compressor 1b, in FIGURE 2, for an automobile air conditioning system. The compressor includes a tapered drive shaft 12 which is adapted to be selectively driven from a pulley 14 which may be driven by a driving pulley connected to the drive shaft of the automobile.

Connected to the tapered end of the compressor shaft 12 is an annular coupling member indicated generally at 16 havinga hub 18 provided with an axially extending tapered opening 20 which receives the tapered end portion of the compressor shaft 12. The coupling member 16 includes a radially outwardly extending annular flange 22.

The pulley 14 is mounted for rotation on the hub 18 of the coupling member and for this purpose a ball hearing indicated generally at 24 is provided on the outside of the hub 18 and is received within a radially inwardly extending flange portion 26 provided on an axially extending cylindrical portion 28 at the inner edge of the pulley. The outer race 30 of the ball bearing is retained in position by a snap ring 32. The inner race 34 of the ball bearing engages a washer 36 which is urged inwardly by a screw 38 extending into a threaded opening at the end of the tapered compressor shaft 1.2. From the foregoing it will be seen that the screw 38 urges the assembly including the coupling member 18 firmly on the taper of the compressor shaft.

At the outer edge of the flange 22 of the coupling member 16 is provided .a clutch plate indicated generally at 4i} which includes a radially inwardly extending flange 42, an axially extending cylindrical portion 44, and the radially outwardly extending clutch portion 46 which will be described subsequently in more detail.

Connecting the radially outwardly extending flange 22 of the coupling member 16 to the radially inwardly extending flange 42 of the clutch plate 50 are a plurality of elongated leaf springs 48 having their outer ends con nected as by rivets 50 to the radially inwardly extending flange 42, and by rivets 52 to the radially outwardly extending flange 22 of the coupling member 16.

As best seen in FIGURES 1 and 3, the elongated leaf springs 48 are disposed to extend substantially tangentially with respect to the periphery of the outwardly extending flange 22 The elongated leaf springs 48 have the flat portions thereof occupying a plane perpendicular to the axis of the shaft 12 and hence, they are adapted to flex readily to permit limited axial displacement of the clutch plate 40 relative to the coupling member 16. At the same time, the leaf springs are adapted to transmit substantial torque between the coupling member and the clutch plate. It will be appreciated that in order to transmit the maximum torque, the leaf springs 48 will be arranged so that they are subjected to tension in transmitting torque from the pulley 14 to the coupling member 16.

As best seen in FIGURES 3 and 4, the rivets 50 are also disposed to support flat abutment plates 54 which overlie the flange 22 and thus limit movement of the clutch plate 40 to the right as seen in FIGURE 2. Due to the presence of the fiat abutment plates 54, springs 48 are always slightly bent and retain the abutment plates p under light pressure against the flat surface of flange 42;.

Referring now to FIGURE 2, it will be observed that see ers clutch portion 46 of the clutch plate is separated from an adjacent annular web portion 56 of the pulley by a relatively small air gap as indicated at 58. The surface of the clutch portion 46 is provided with circular recesses for receiving a friction material such for example as asbestos or the like, adapted to provide frictional driving engagement between the clutch plate and the pulley. It will also be observed that the radially outward edge of the clutch portion 46 of the clutch plate is closely spaced to the inner surface 6t of the rim portion 62 to provide a small air gap as indicated at 64.

Located within an annular chamber defined between the surface 60 of the pulley and the outer surface of the cylindrical portion 44 of the clutch plate is a field winding 66 received within a field coil housing 68. The field coil housing 68 is arranged to have relatively small air gaps 7i) and 72 to the inner surface 60-of the pulley and the outer surface of the cylindrical portion 44 of the clutch plate.

The field coil housing 68, the clutch plate and at least the clutch portion 56 of the pulley 14 are formed of magnetic material. Attention is particularly drawn to the relatively great air gap indicated at 74 between the end of the coil housing 68 and the adjacent surface of the clutch portion 46 of the clutch plate for a purpose which will presently appear.

The field coil housing 68 is rigidly supported by an annular bracket 76 bolted to an end of the compressor as indicated at 78. The field coil housing 68 is thus maintained stationary and there is no problem of providing brushes or the like to complete an electric circuit therethrough.

Due to the relative dimensions of the air gaps separating the field coil housing 68 from the pulley 14 and the cylindrical portion 44 of the clutch plate, the lines of magnetic flux pass from the field coil housing to the pulley 14 and the clutch portion 46 of the clutch plate 46. However, means are provided to insure that the flux traverses the air gap between the clutch portion 46 and the adjacent annular portion 56 of the pulley a plurality of times so as to increase the force pressing the clutch plate against the pulley. This means comprises the arcuate openings 80 which are provided in the portion 56 of the pulley and similar arcuate openings 82 formed in the clutch portion 46 of the clutch plate. As a result of this arrangement the closed path which the flux defines from the coil housing 68 is illustrated by the small broken arrows at the bottom of FIGURE 2.

The use of the elongated leaf springs provides a very simple connection between the coupling member 16 and the clutch plate 40 which permits movement under relatively small forces of the clutch plate axially into engagement with the annular clutch portion 56 of the pulley, while at the same time providing relatively powerful means for transmitting torque between the members. It is also important to provide for initial movement of the clutch portion 46 into engagement with the clutch portion 56 of the pulley so that the air gap at 58 is maintained at a small dimension with considerable accuracy. This is accomplished by the provision of the abutments 54 which prevent movement of the clutch portion 46 of the clutch plate away from the clutch portion 56.

As best seen in FIGURES 3 and 4, each flat abutment plate 54 is positioned between the end of each fiat leaf spring 48 and the flat surface of the flange 42 of the clutch plate. The other end of each leaf spring 48 is connected flat against the flat surface of the radially extending flange 22 of the coupling member 16. Accordingly, the abutment prevents the leaf springs from becoming straight, and the clutch member is thus held against axial movement with light spring pressure when the clutch is disengaged.

Referring now to FIGURES and 6 there is illustrated a second embodiment of the present invention which incorporates some improved features. In this embodiment of the invention a portion of the compressor is indicated in dotted lines at 99 to which is connected a rigid annular bnacket 92 carrying the field coil housing 94- in rigidly fixed location. Extending from the cornpressor is the end of a drive shaft 96 to which is secured a coupling member 98 having a hub portion 109 keyed as indicated at 102 to the compressor shaft and having a radially outwardly extending flange portion 1164. Connected to the flange 164 is a clutch plate indicated generally at 166, the connection being by elongated leaf springs 168 corresponding to the leaf springs 48 illustrated in the first embodiment of the invention. The inner ends of the leaf springs are connected to the flange by rivets 110 and the outer ends of the leaf springs are connected to the clutch plate 166 by the rivets 112 which also carry stop elements 114 effective to limit axial movement of the clutch plate 106 away from its position of clutching engagement. It will be observed that the interposition of the stop elements 111 causes the leaf springs 16% to remain slightly bowed so that in the unclutched position there is a slight spring tension holding the stop elements 114 against the surface of the flange 1194. This has the effect of preventing vibration and causing silent operation.

Driving means herein illustrated as a pulley 116 is provided connected by a ball bearing to the hub portion of the connector 98. The inner race 118 of the ball bearing is pressed to a reduction portion of the hub 100 and the outer race 12%" is provided with a press fit into a recess at the inner side of the pulley 116. Balls 122 are provided intermediate the races and a snap ring 124 may be provided to lock the outer race in position.

The pulley 116 includes a clutching web portion 126 reinforced by generally radially extending but preferably slightly circumferentially inclined ribs 128, the inner surface of the web portion, as indicated at 130, being a fiat radially disposed clutching surface. The rim of the pulley 116 extends axially and has an inner cylindrical surface 132 spaced with minimum clearance from the Outer surface of the field coil housing 94. It may be mentioned at this time that the clutch plate 166 includes a generally cylindrical portion 134 of substantial cross-section to provide a good path for magnetic flux, the inner surface of which as indicated at 136 is spaced with minimum clearance with respect to the inner surface of the field coil housing 94. The field coil windings are indicated at 138.

The clutch plate 166 includes a radially extending clutch portion 141 having a flat surface disposed in a radial plane which is modified as will now be described. The operating surface of the clutch portion 140 includes relatively deep annular recesses 142 and 144 adapted to receive a friction material indicated at 146 such for example as an asbestos brake compound. Upon initial production of the clutch plate, the friction material 146 is provided so that it does not extend beyond the surface of the clutching portion 140. In fact, to insure that it does not extend beyond the clutching surface, it is preferably recessed slightly below the surface so that it does not come into frictional engagement with the clutch surface of the pulley until the parts are worn in.

In order to provide a specific path for magnetic flux which interlinks the clutch portions of the pulley and the clutch plate, a continuous annular groove or recess 148 is provided in the active surface of the clutch portion of the pulley. In the flange or clutch portion of the clutch plate, elongated ci rcum'ferentially extending openings 150 are provided. As a result of the relatively deep groove or recess 148 and the elongated circumferentially extending openings 156, the magnetic flux resulting from the passage of current through the windings of the field coil 138 is positioned to follow a path represented by the short arrows at the top of FIGURE 5. The flux is forced to follow this path due to the spacing between the field coil housing 94, the adjacent portions of the pulley 116,

6 and the clutch plate 106. It will be observed that the establishes magnetic attraction forces urging said clutch magnetic flux links the clutch surfaces of the pulley and member axially outwardly away from said coil and clutch plate at three distinct annular zones. housing.

A very important feature of the present invention is 2. A clutch construction as defined in claim 1 in which the further modification of the clutch surface of the 5 the clutch surface of said clutch member is provided with clutch plate 106 as illustrated in FIGURES 5 and 6. It recesses, friction material in said recesses for providing will be observed that the clutch surface of the Cl c frictional driving engagement between the clutch surfaces, plate is modified by shallow relief at its outer periphery the friction material initially being provided slightly beas indicated at 152 and at its inner periphery as indicated low the clutch surface of said clutch member so as to at 154, and further, intermediate the nn r nd Outer require some wear of the clutch surface of said clutch ges thereof as indicated at 156. This relief is relamember before the friction material can contact the clutch tively shallow as for example about ten to fifteen thousurface f the outer rotary member. sandths. It has the effect of restricting the cross-sectional 3. A clutch comprising a stationary support, a rotary ar a of th path f r m g fi directly at a p e face shaft, 21 first rotary member fixed to said shaft and havwhich increases the magnetic attraction between the pole ing a first flat radially extending surface, an annular clutch faces as a result of the act that the magnetic attracti n member surrounding said rotary member and having a varies substantially as the square of the flux density. second fiat radially extending surface adj t id fi t At the same time, the relief areas are kept as shallow as surface, a second rotary member, means mounting said possible in order to introduce a minimum additional resecond rotary member for rotation about the axis of said luctance to the flux path. In a specific case, excellent shaft, said clutch member and said second rotary member results were obtain d when the active area of the pole having generally radially extending clutch surfaces, means face was reduced approximately one-third by the proviconnecting said clutch member to said first rotary memsion of the shallow relief. It is believed that a reduction her for rotation therewith and for limited movement relaof pole face area by an amount between one-quarter and tive thereto axially of said shaft to effect engagement one-half is most desirable. 2 and disengagement between said clutch surfaces, said While the present disclosure includes a pulley it will means comprising normally flat leaf springs, means conof course be apparent that other driving means such for necting the end portions of each of said springs to said example as a gear could be substituted therefor. first rotary member and said clutch member in circum- While the detailed disclosure herein relates to a clutch, ferentially angularly spaced relation and with the end it will of course be apparent that certain aspects of the portions of the springs parallel to said radially extending present invention are applicable to other magnetically surfaces thereof, abutment means acting between said a' tuated devices such for example as a magnetic brake. first rotary member and said clutch member and engage The drawings and the foregoing specification constiable upon movement of said clutch member away from tute a description 0" the improved magnetic clutch structhe clutch surface of said second rotary member to preture in such full, clear, concise and exact terms as to vent the end portions of said springs from occupying the enable any person skilled in the art to practice the insame plane so that said leaf springs are bent in a direcvention, the scope of which is indicated by the appended tion tending to produce further movement of said clutch claims. member away from the clutch surface of said second What we claim as our invention is: rotary member, and electro-magnetic means effective when l. A magnetic clutch comprising a stationary support, 40 energized to move said clutch member toward the clutch an inner rotary member carried thereby, a clutch mernsurface of said second rotary member. her, means connecting said clutch member to said rotary 4. A clutch as defined in claim 3 in which said flat member for limited axial movement relative thereto and radially extending surfaces face in the same direction, and for transmission of torque therebetween, said clutch memin which said abutment means comprises a flat abutment her having an axially extending tubular portion surroundplate secured to the fiat radially extending surface of one ing said rotary member and provided with a cylinof the members to which said leaf springs are secured drical outer surface and a generally fiat annular portion between and in parallelism to the end portion of a leaf extending radially outwardly from the axially outer end spring connected to said one member and said flat radialof said tubular portion and having a flat annular axially extending surface. ly outer clutch surface, an outer rotary member having 5. A clutch as defined in claim 3 in which said fiat a tubular portion provided with a cylindrical inner surradially extending surfaces face in the opposite direction face and having a radially extending portion provided and in which said abutment means comprises a fiat abutwith a fiat radially inwardly extending inner clutch surment plate secured in parallel relation between the radialface engageable by the fiat clutch surface of said clutch ly outer flat surrace and the end of one of said leaf member upon axially outward movement thereof, an springs in a position to engage the flat radially extendelectroma net coil, an annular magnet housing of U- ing surface of the member to which the other end of said shaped cross-section carried by said stationary support leaf spring is secured. having an outer cylindrical surface closely spaced from 6. A clutch comprising a stationary support, a rotary the inner cylindrical surface of said outer rotary member shaft, a first rotary member fixed to said shaft and havto provide a relatively low reluctance magnetic flux path ing a first fiat radially extending surface, an annular therebetween and an inner cylindrical surface closely clutch member surrounding said rotary member and snaced from the outer cylindrical surface of said clutch having a second flat radially extending surface adjacent member to provide a relatively low reluctance magnetic said first suiface, a second rotary member, means mountflux path therebetween and axially outer end walls spaced ing a d second rotary member for rotation about the axi substantially from the axially inner surface of the radialof said shaft, said clutch member and said second rotary ly outwardly extending portion of said clutch member, member having generally radially extending clutch surthe radially outer edge of said radially outwardly extendfaces, means connecting said clutch member to said first ing portion of said clutch member being spaced substanrotary member for rotation therewith and for limited tially from the inner cylindrical surface of said outer movement relative thereto axially of said shaft to effect rotary member to provide a relatively high reluctance engagement and disengagement between said clutch surmagnetic flux path therebetween, the said clutch surfaces faces, said means comprising normally fiat leaf SPIIHYS, of said clutch member and outer rotary member being means connecting the end portions of each of said SPIIHOS ielatively movable between engaged operating position to said first rotary member and said clutch member in and closely spaced inoperative position whereby all flux circumferentially angularly spaced relation and. with the established by said coil links, said clutch surfaces and end portions of the springs parallel to said radially extending surfaces thereof, recesses in the clutch surface of said clutch member, friction material in said recesses for providing frictional driving engagement between the clutch surfaces, the friction material initially being provided slightly below the clutch surface of said clutch member so as to require some Wear of the clutch surface of said clutch member before the friction material can contact the clutch surface of the second rotary member, and electro-magnetic means effective When energized to move said clutch member toward the clutch surface of 10 said second rotary member.

References Cited in the file of this patent UNITED STATES PATENTS Payne Dec. 16, 1924 15 8 Payne Mar. 22, Payne Apr. 29, Lear et al Dec. 23, Thompson Mar. 30, Oetzel June 10, Russell Aug. 12, Winther Mar. 13, Gamundi Mar. 27, Cunningham Mar. 10, McGuftey et al. Apr. 7, Harting Nov. 24,

UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No. 310361679 y 2 Alfred F. Millington et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In the grant, lines 2 to 4, for "assignors to Novi Equipment Company, of Novi, Michigan, a corporation of Michigan," read assignors, by mesne assignments, to Lewis W. Welch, trustee,"; line 13, for "Novi Equipment Company, its successors" read Lewis W. Welch, as trustee, his successors in the heading to the printed specificati lines 4 and 5, for "assignors to Novi Equipment Company, Novi, Mich., a corporation of Michigan" read assignors, by mesne assignments, to Lewis W. Welch, -trustee Signed and sealed this 6th day of November 1962.

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents 

